Recently, polycarbonate resins and polyester resins derived from dihydroxy compounds having a fluorene ring in the side chain thereof have been reported, and making full use of the fluorene ring-derived characteristics such as optical properties and heat resistance thereof, those resins have been proposed as materials useful for optical applications (for example, see PTL 1). PTL 2 and 3 disclose as follows: When the content of the fluorene ring-having repeating unit in a polycarbonate resin is controlled to fall within a specific range, the stretched film formed of the polycarbonate resin exhibits reversed wavelength dispersion characteristics of such that the retardation of the film is smaller at a shorter wavelength, and therefore, the film has excellent performance as a retardation film. Such a retardation film exhibiting so-called reversed wavelength dispersion characteristics of such that the retardation of the film is smaller at a shorter wavelength can have ideal retardation characteristics at each wavelength in a visible light region, and is therefore useful as a circularly polarizing film for prevention of outer light reflection and viewing angle correction in image display devices.
PTL 4 discloses as follows: When the content of the fluorene ring-having repeating unit in a polyimide resin is controlled to fall within a specific range, the stretched film formed of the polyimide resin exhibits flat wavelength dispersion characteristics of such that the retardation of the film changes little in a broad area from a short wavelength side to a long wavelength side, and therefore, the film has excellent performance as a retardation film. Such a retardation film exhibiting flat wavelength dispersion characteristics is useful for correcting VA (vertical alignment)-mode liquid crystals.
As dihydroxy compounds having a fluorene ring in the side chain thereof, well used are 9,9-bis(4-(2-hydroxyethoxyl)phenyl)fluorene and 9,9-bis(4-hydroxy-3-methylphenyl)fluorene described in PTL 2 and 3. On the other hand, PTL 4 discloses a diamine compound having a fluorene ring in the side chain thereof, and describes a stretched film of a polyimide resin using the compound. PTL 5 discloses a diester compound having two fluorene ring in one molecule, and describes a polyester resin using the compound. PTL 6 discloses a dihydroxy compound and a diester compound having two fluorene rings in one molecule, and describes a stretched film of a polyester resin using the compound.